Seismic data collected on land, at sea, or on the seabed forms an integral part of oil exploration. Seismic data comprises a wavefield generated from a seismic source or sources traveling downward through the earth, being reflected back to the earth's surface from rock strata, then being recorded onto digital tape via a seismic receiver or receivers. The digitally-recorded seismic data is then passed through various algorithms or processes in a computer to build a digital image or model of the earth's subsurface.
In order to build an accurate image or model of the earth's subsurface from the recorded seismic data, an accurate knowledge of the velocity at which the wavefield travels through the various rock strata is needed. This knowledge of the velocity in the rock strata can be gained from the recorded seismic data itself according to various techniques.
Having acquired the relevant knowledge of velocity, velocity fields are derived. The velocity fields are necessary for the various processes that need to be applied to the seismic data in order to build the digital image or model of the earth's subsurface. Various methodologies exist to derive the velocity fields having once measured the velocities. For example, two previously published articles describe a methodology to derive a pre-stack time and/or depth migration velocity field from constant velocity pre-stack time migrated data cubes. (See, Interpretive Imaging Of Seismic Data, Yilmaz et al., Leading Edge (February 2001) and Seismic Data Analysis-Processing, Inversion, And Interpretation Of Seismic Data, Yilmaz, SEG (2001).)
The ever-continuing requirement for reduced process turn-around and early delivery of the digital image or model of the earth's subsurface has led to improvements in the production workflow for velocity field derivation. It is of interest in the art to develop improved methods of seismic data processing using velocity field derivation.